1. Field of the Invention
The present invention relates to a powder conveying device, and more particularly to a powder conveying device and an image forming apparatus having the same.
2. Description of the Related Art
A powder conveying device is used to convey powder composed of fine particles such as, for example, toner particles. Generally, a powder conveying device may be used in manufacturing equipments for various products to convey powder type row material, or in a device that uses powder material in operation to convey a predetermined amount of powder.
An example of a powder conveying device is described in U.S. Pat. No. 7,076,192 to Tsuda et al. (“Tsuda”), which discloses a powder conveying device employed in an electrophotographic image forming apparatus to convey toner. The powder conveying device disclosed by Tsuda includes a coil spring (a rotary type feeding member) placed inside a conveying pipe and a driving device to rotate the coil spring. Toner in the conveying pipe is conveyed toward an outlet by the rotation of the coil spring.
The coil spring type powder conveying device, e.g., disclosed by Tsuda, may, unfortunately, cause unpleasant noise from the coil spring contacting against the inner surface of the curved conveying pipe while rotating inside, and being elastically deformed by the curved shape of, the conveying pipe. Further, a significantly large space may be required for forming the curved conveying path of the toner, which increases the overall size of the image forming apparatus.
Another type of powder conveying device may utilize an auger having a helical-shaped blade, by the rotation of which the toner particles may be conveyed in a conveying path. Examples of the auger type powder conveying devices are described in, e.g., Japanese Patent Laid-open Publication No. 2007-57790 to Yoshinori (“Yoshinori”) and Japanese Patent Laid-open Publication No. 2007-17464 to Tomoyuki (“Tomoyuki”).
These auger type powder conveying devices, e.g., of Yoshinori or Tomoyuki, because they require a motor to rotate the auger and a gear train to transmit the driving force, unfortunately, also tends to be expensive and to increase the overall size of the image forming apparatus.